title: Geometry of the randomized evidence for treatments of pulmonary hypertension.
abstract: OBJECTIVE
  We studied the entire agenda of randomized clinical trials in pulmonary hypertension (PH) using sociological methods. We explored the geometry of the PH network to interpret the evidence on multiple competing treatments for the same indication.
  
  
  METHODS
  We searched MEDLINE, Embase and Cochrane Library Databases for published studies. We queried clinicaltrials.gov and WHO International Clinical Trials Registry platform for non-published studies.
  
  
  RESULTS
  We found 75 randomized trials (41 published [n = 4136 participants] and 34 registered unpublished [planned n = 3470 participants]). Of the published randomized studies, all used placebo as the comparator arm except for two nonindustry-sponsored comparisons between phosphodiestearase-5 (PDE-5) inhibitors and endothelin receptor antagonists (ERA), and one study comparing two different regimens of treprostinil. Similarly, only five unpublished/ongoing trials used an active PH treatment as comparator (PDE-5 inhibitors versus ERA (n = 3), different doses of sildenafil (n = 1) and two formulations of epoprostenol (n = 1). Of the 75 trials, 47 were sponsored by the manufacturer of the tested active product(s), and only two trials were sponsored by two companies comparing their products.
  
  
  CONCLUSIONS
  The relative merits of different treatment options are not directly known, as there are very few head-to-head comparisons. A limited number of ongoing studies are using active FDA-approved PH-treatments for comparison. This lack of information can be overcome by carefully designing comparative effectiveness trials.
authors.affiliation: Department of Pulmonary, Allergy, and Critical Care Medicine, Respiratory Institute, Cleveland, OH, USA.
authors.forename: Adriano R
authors.initials: AR
authors.lastname: Tonelli
authors.forename: Joe
authors.initials: J
authors.lastname: Zein
authors.forename: John P A
authors.initials: JP
authors.lastname: Ioannidis
mesh_terms: D017277:Drug Approval; D006801:Humans; D006976:Hypertension, Pulmonary / Q000188:drug therapy*; D016032:Randomized Controlled Trials as Topic; D014481:United States; D014486:United States Food and Drug Administration
keywords: Pulmonary hypertension; Treatment